The insulin-like growth factor-I receptor (IGF-IR) is a key mediator of fetal development and cell proliferation, and serves as an inhibitor of programmed cell death. Ethanol inhibits IGF-I-mediated cell proliferation and reverses the survival action of the IGF-I. These functional effects correlate with the strong inhibition by ethanol of IGF-IR tyrosine autophosphorylation and the phosphorylation of key signaling mediators such as insulin-related substrate 1 (IRS-1). The mechanism by which ethanol interferes with IGF-IR activation is unknown. It is hypothesized that ethanol interferes directly with the tyrosine kinase activity residing within the cytoplasmic beta domain of the IGF- IR. Functional studies suggest that the phosphorylation of specific tyrosine residues within the beta domain is preferentially inhibited by ethanol. To address these issues, purified IGF-IR will be used to study tyrosine kinase activity in vitro. The effect of ethanol on the requirements for ligand, ATP, and substrate will be determined with respect to the kinetics of autophosphorylation and kinase activity for exogenous substrates. The effect of ethanol on the phosphorylation of specific tyrosines within the beta domain will be determined by tryptic mapping and Edman sequencing. Ethanol-sensitive sites on the IGF-IR beta domain will be functionally mapped by site-directed mutagenesis at specific tyrosine residues and other regulatory domains. The identification of ethanol-sensitive sites on the IGF-IR will be used to examine the effect of ethanol on the phosphorylation of key signaling mediators that are bound and/or phosphorylated by the IGF-IR including IRS-1, Shc, Grb-10, and phosphatidylinositol-3 kinase. Overall, these studies are designed to unravel the interaction of ethanol with the IGF- IR, and have broad implications for the pathogenesis of fetal alcohol syndrome, and for tissue injury in the setting of chronic alcoholism.